Runner-Up

Aaron McFarland
Knoxville, TN USA

PalmScope is a hardware and software project implementing the functionality of a portable oscilloscope, spectrum, and logic analyzer using a PC- or PalmOS-based PDA for display. The hardware communicates serially with either the PDA or PC. The software allows the user to view signals up to 120 VAC versus time or frequency (FFT). With a maximum sample rate of 40 Msps and a bandwidth of 2 MHz, it is possible to view a wide range of input signals with great accuracy.

Software

PalmScope has two operational modes: Signal mode and Logic Analyzer mode. Both modes are controlled through software by the user. Signal mode is used in two different ways by the user interface: as an oscilloscope or spectrum analyzer. When functioning as either, it is possible to adjust the time and voltage scale. In Logic Analyzer mode, the user has control over time scale and trigger value. In all modes, there are cursors available for precise identification of the incoming signal’s amplitude, frequency or value.

Hardware

Designed for portability, the PalmScope makes an excellent field unit. The design has a low part count, using only eight core chips in both the analog and digital modules. The ATMEGA103L orchestrates the operation of the digital hardware, the gain of the analog front end, and negotiates the serial link with the PDA or PC.

Operation

Simply, a signal is input to a digitally controlled instrumentation amplifier and conditioned appropriately to a level suited for input the analog-to-digital converter (ADC). The AVR waits for a request of samples from the controlling software, then signals the FPGA to begin writing data from the ADC to the 1-kB FIFO RAM. To simplify the board layout (one layer) for a hobbyist’s budget, the data bus is routed through the FPGA. This also facilitates the hardware triggering in Logic Analyzer mode. When the FIFO registers as full, the AVR sends the data over the serial connection and awaits another sample request before acting further.

Feature Summary